RU2478436C2 - Plant and method for water cleaning by flotation - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention may be used in chemical industry. Proposed plant comprises, at least, one water intake zone 31, zone 32 of water mixing at pressure and water mixing at vacuum, flotation zone 35 separated from mixing zone 32 by wall, and cleaned water draw-off zone 36 at the bottom of said flotation zone 35. Mixing zone 32 comprises, at least, one water injection nozzle 40, 91, 92 arranged nearby panel 33. At least, one part of the latter has holes 331 to separate intake zone 31 and mixing zone 32.

EFFECT: better contact between treated and injected water, higher quality of clarified water.

34 cl, 10 dwg

Description

Technical field

The scope of the invention is installation for clarification of treated water. More specifically, the invention relates to water treatment plants using a flotation process.

Prior art

Installation for flotation water treatment according to known technology is shown in figure 1.

Such a clarification unit includes a coagulation zone and a flocculation zone (not shown). In the coagulation zone, one or more coagulators (for example, aluminum polychloride, aluminum sulfate, iron chloride, etc.) are introduced into the treated water before this water is sent to the flocculation zone.

Flocculation is a physicochemical process, the purpose of which is to change the state of colloidal particles in suspension in water so that the particles coagulate with each other and fall out in the form of flakes.

As shown in figure 1, such a flotation treatment plant includes a mixing zone 1 in the lower part, into which the treated water is introduced in the form of an upward flow, which was previously subjected to coagulation and flocculation (arrow A), and then water under pressure (arrow B) c subsequent depressurization so that microbubbles of air are formed. As shown by arrow C, the air bubbles that are formed in this way allow you to bring to the surface of the mixing zone all the particles in suspension, collected on the air bubbles. A mixture of particles agglomerated on air bubbles forms a layer of bubbles 2, or foam, which moves to the surface of mixing zone 1 and flotation zone 3.

These particles collected on air bubbles can then be removed (arrow D) from the top of flotation zone 3.

The selection of clarified water is performed in the lower part of the flotation zone 3, for example, using a perforated pipe 4 connected to the pipelines 5, or by any other means.

The disadvantages of the known technology

The disadvantages of this known technology are associated with the design of the mixing zone. Indeed, this mixing zone does not provide uniform contact of the treated water, which was previously coagulated and flocculated, then the water was under pressure, followed by depressurization over the entire horizontal section of the mixing zone. This lack of uniform contact is observed regardless of the amount of treated water, the quality of the treated water and the magnitude of the flow of water under pressure and then under vacuum.

Such a lack of uniform contact as a whole leads to a disruption of the agglomeration of particles in suspension in the treated water with air microbubbles, which reduce the efficiency of the water treatment.

Another disadvantage of this known technology is associated with the design of the flotation zone. Indeed, a substance in suspension, agglomerated with air bubbles, leads to the appearance of reverse flows in the intake zone of purified water.

Therefore, this phenomenon can cause the suspension of matter, agglomerated with microbubbles, into the stream of clarified water. Therefore, the collected clarified water contains impurities, and the efficiency of the device is thus reduced.

In addition, a suspended layer of agglomerated with air bubbles that forms on the surface of the flotation zone can reach a height close to the height of the flotation zone, which, together with the phenomenon of reverse flows, promotes the transfer of impurities into the water in the intake zone of purified water.

These return flows are shown in FIG. 2, which shows the velocity vectors 21 of the water flow in the flotation zone. In this figure 2 it can be seen that the purified water tends to rise to the upper part of the flotation zone, where a layer of air bubbles is located. The clarified water is then mixed with air bubbles, initially loaded with particles in suspension in the treated water, before being transferred to the base of the flotation zone.

OBJECTS OF THE INVENTION

The invention, in particular, aims to overcome the disadvantages of the known technology.

More specifically, the aim of the invention is to provide a method of water treatment, which allows to optimize the process of clarification of water by flotation.

Another objective of the invention is to provide a method of clarification of water by flotation, which allows you to get a homogeneous mixture of treated water and water under pressure and then water under vacuum.

The invention also aims to implement such a method, which allows to prevent the occurrence of reverse flows in the intake zone of purified water.

Another objective of the invention is to provide a method that, when implemented, is reliable, simple and economical.

Description of the invention

The invention relates to an installation for flotation treatment of water containing at least:

- one inlet zone for the treated water, which is previously subjected to coagulation and flocculation;

- one zone of mixing water under pressure and then water under vacuum with the specified treated water;

- one flotation zone, separated by a wall from the specified mixing zone;

- one zone of intake of purified water provided in the lower part of the specified flotation zone.

According to the invention, said mixing zone has at least one spray nozzle for spraying said water under pressure, said spray nozzle being located near the panel, at least one part of which has a perforation, and which separates said entrance zone and said mixing zone .

Thus, the invention consists of inserting a perforated panel between the inlet zone of the treated water and the mixing zone. Passing the treated water through a perforated panel allows homogenizing and fragmenting the stream of treated water. This ensures uniform contact between the treated water and the air microbubbles formed in the mixing zone, creating pressure and then depressurizing the water over the entire horizontal section of the mixing zone, which improves particle agglomeration in suspension with microbubbles of air in the treated water.

In addition, the invention allows to neutralize the hydraulic slip, which reduces efficiency due to insufficient contact between the particles in suspension and air bubbles.

Therefore, the creation of such a perforated panel according to the invention allows to optimize the processing of water by flotation and to improve the quality of clarified water collected at the end of the treatment cycle.

According to the most advantageous characteristic, this panel is installed mainly horizontally.

In this case, the flow of treated water is mainly a downstream flow through the panel. If the flakes that are formed during coagulation / flocculation are persistent, pressurized water is preferably sprayed countercurrent to the treated water. Spray nozzles are generally arranged vertically so that water is sprayed under pressure in the initially incident stream.

If the flakes that have formed are brittle, the nozzles are placed so that the water under pressure is sprayed parallel to the flow of the treated water, i.e. in such a way that water is sprayed under pressure in accordance with the initially upward flow.

According to another advantageous characteristic, said panel is mounted mainly vertically.

In this case, the spray nozzles are arranged substantially horizontally so that pressurized water is sprayed in the initially horizontal stream. Only the spraying direction is different (parallel flow or counterflow) depending on whether the flakes are brittle or resistant.

In other conditions, the panel may be tilted.

According to a preferred embodiment, the water treatment plant according to the invention comprises a plate forming a mudguard substantially parallel to said panel, which extends between said panel and said nozzle and in which at least one part has first openings.

The use of such a plate forming a mudguard allows to improve the fragmentation of the flow of treated water and, thus, to ensure uniform contact between the microbubbles of air and the treated water in the mixing zone.

Preferably, said first openings of said plate are located in the solid part of said panel.

This allows you to create baffles through which the treated water must pass before it enters the mixing zone. The presence of such baffles also improves fragmentation of the treated water stream.

Advantageously, said plate would have second openings that are located above said perforation of said panel.

These second openings, also called cleaning openings, optimize the homogenization of the treated water stream.

According to a preferred embodiment of the method described herein, each of said spray nozzles is disposed substantially along the axis of one of said perforations of said panel.

This allows you to get the optimal mixture between the flows of treated water and water under pressure. However, according to an alternative solution in which the perforations of the panels are relatively small, a correspondence between each spray nozzle and the perforations of the panel is not required to obtain a satisfactory mixture.

It is useful when the water purification apparatus according to the invention includes first and second distribution networks of said pressurized water in accordance with two different flow rates.

This approach makes it possible to spray water under pressure depending on the flow rate Q1 through the first grid, depending on the flow rate Q2 through the second grid and depending on the flow rate Q3 equal to the sum of the flow rates Q1 and Q2 when these two networks operate simultaneously. The flow rate can be selected, for example, depending on the volume of treated water and / or depending on its quality. Preferably, said nozzle is connected to said first and second distribution networks.

Such nozzles, also called double nozzles, because they are connected directly to these two nets, can also be used with the splash guard plates. However, their use is recommended when the mudguard is not used, and each of the nozzles passes along the axis of perforation of the panel.

According to alternative solutions, said nozzles belong to two categories of nozzles, wherein the first category of nozzles is connected to said first network and the second category of nozzles is connected to said second network.

Such spray nozzles can preferably be used when there is a shield forming a mudguard, or when the perforations of the panel are small in diameter, preferably between two and thirty centimeters.

Preferably, said nozzle comprises two perforated plates placed opposite each other.

Thus, these nozzles include two perforated walls, also called pressure relief walls, which expose the pressurized water to the first rapid pressure release and then to the second low pressure release, which atomizes the water, accompanied by microbubbles of air. In addition, spraying helps to prevent high breaking rates at the spraying stage.

According to preferred characteristics, said nozzles have a lower diverging circuit.

The use of a lower divergent circuit makes the spraying process more reliable.

Preferably, the diverging contour is flat and forms a vertical angle from 0 to 20 °.

Preferably, the diverging contour is curved.

According to a preferred aspect of the invention, the upper part of said wall separating said mixing zone from said flotation zone includes a part inclined at an angle in the direction of said flotation zone.

In this case, the value of the specified angle preferably lies in the range from 120 ° to 175 °.

According to another preferred embodiment, said wall separating said mixing zone from said flotation zone has an upper portion curved in the direction of said flotation zone.

In this case, said curved portion preferably has a radius of 0.1 to 1 meter.

The execution of such inclined or curved parts can, in particular, facilitate the passage of water from the mixing zone to the flotation zone.

Preferably, said flotation zone has a plurality of baffles extending substantially vertically above said sampling zone.

The use of such partitions allows the fragmentation of clarified water, which flows to the base of the flotation zone, and prevents the appearance of reverse flows. This helps prevent mixing of clarified water with a layer of air bubbles; particles originally contained in the treated water are carried.

Preferably, at least one of these partitions would have at least one upper part inclined at an angle or have a curved profile.

Preferably, the angle has a value from 120 ° to 240 °.

These inclined or curvilinear parts allow to improve the breakdown of reverse flows in the area of intake of purified water.

Preferably, said partitions would have a height of 30 to 300 cm. According to another preferred embodiment of the invention, said partitions are located close to each other at said wall separating said mixing zone from said flotation zone.

This, in particular, can prevent the formation of induced flow rotation between the two plates.

Preferably, these partitions would be separated from each other by a distance of from 20 to 300 cm

Preferably, said intake zone would have means for collecting clarified water associated with means for collecting clarified water.

According to a preferred embodiment, the water treatment plant according to the invention has means for producing said water under pressure.

Preferably, said means for producing water would be connected to said means for taking clarified water and to an air supply source.

Water under pressure can thus be obtained using clarified water taken from the outlet of the installation using the technique described here. Alternatively, pressurized water can also be obtained using treated water, which is preferably not coagulated and free from flakes.

Preferably, the water purification apparatus according to the invention includes a purifier which can be located in the upper part of said flotation zone.

This cleaning agent allows you to simply and efficiently remove layers of air bubbles.

The invention also relates to a method of flotation water treatment, which consists in transferring water to the installation according to the method described here, and in the supply of water in an upward flow to the specified mixing zone, the transfer of the specified treated water through the specified perforated panel, and the flow of the specified water under pressure using the specified spray nozzles (nozzles) so as to form air bubbles capable of transferring particles in suspension from the specified treated water to the surface of the specified zone mixing.

According to a preferred aspect of the invention, said flow of said pressurized water is initially upward.

According to another preferred aspect of the invention, said stream of said pressurized water is initially downward.

According to yet another preferred aspect of the invention, in the method described herein, said stream of said pressurized water is initially horizontal.

Indeed, depending on the quality of the treated water, more or less persistent flakes can be formed during the coagulation process. The method of use of the nozzle depends on the resistance of the flakes. If the flakes are brittle, forward flow is used to create a sufficient breaking speed. In the case when extremely persistent flakes are formed during the loss of flakes during the coagulation process, a counterflow is necessary.

Thus, depending on whether the panel extends substantially horizontally or vertically, and whether the flakes are brittle or resistant, the nozzles can be mounted so that the pressurized water is atomized forward flow or countercurrent to the treated water.

In another alternative, nozzles can also be mounted mainly horizontally when the panel is also basically mounted horizontally.

Preferably, the flotation water treatment method according to the invention includes the step of selecting one of said values for said flow rate of said water under pressure, depending on the flow rate of said treated water and / or the quality of said treated water.

Therefore, the method according to the invention can be modified and can be adapted to a large number of situations.

According to another preferred embodiment, the flotation water purification method according to the invention consists in using said purification means to remove said particles collected by said air bubbles outside said flotation zone,

List of drawings

Other features and advantages of the invention will become more apparent upon reading the following description of preferred embodiments of the invention, presented for information only, and not limitation, and the attached drawings, in which:

- figure 1 - installation for water purification by known technology;

- figure 2 - the vectors of the fluid flow rate in the installation shown in figure 1;

- figure 3 is a first embodiment of a water treatment plant according to the method shown here, in which a perforated panel separates the input zone of the treated water from the mixing zone;

- figure 4 is a partial view of an alternative installation of figure 3, in which several spray nozzles are used without connection with perforation of the perforated panel;

- figure 5 is a diagram of a spray nozzle, which can be connected to two networks for spraying water under pressure with different flow rates;

- figure 5 bis is an alternative solution for the lower circuit, in which the nozzle shown in figure 5 can be used;

- Figures 6 and 6 bis represent two architectures of a pressure water distribution network using the nozzles shown in Figure 5;

- figure 7 is a second example embodiment of a water treatment plant according to the invention, which includes a hole plate inserted between the spray nozzles and the perforated panel;

- figure 8 is a partial view of an alternative design of the installation shown in figure 7, which uses several rows of nozzles;

- Figure 8 bis is another alternative plate design forming a mudguard;

- figure 9 is an example of the architecture of a distribution network of pressurized water, in which the nozzles of the first category are connected to the spray network of pressurized water according to the first flow rate, and the nozzles of the second category are connected to the spray network of water according to the second pressure flow rate of water;

- figure 10 represents the vectors of the fluid flow rate in the installation according to the method shown here.

Description of embodiments of the method described herein

A brief explanation of the principle of the method described here

The main principle of the invention is based on the use of a flotation water treatment plant containing a perforated panel that separates the inlet zone of pre-coagulated and flocculated treated water from the mixing zone of the treated water with pressurized water, and then with water under vacuum, the mixing zone containing one or more spray nozzles for spraying water under pressure.

The presence of a perforated panel allows homogenizing and fragmenting the flow of treated water in the mixing zone. Such fragmentation provides uniform contact between the treated water and the air microbubbles formed in the mixing zone along the horizontal section of the mixing zone. Thus, the use of such a perforated panel allows us to optimize the process of clarification of water by flotation.

In addition, the installation according to the invention further includes a flotation zone containing partitions located at some distance from each other and which are mainly mounted vertically and parallel to each other.

The use of such partitions in the flotation zone allows you to break the flow of fluid flowing in the flotation zone. This helps prevent reverse flows, especially in the lower part of the flotation zone, i.e. prevents contact of clarified water with a layer of bubbles on the surface of the flotation zone. Thus, it is possible to prevent or at least limit the transition of particles in suspension, associated with air bubbles, into the intake zone of purified water.

The use of such partitions prevents the penetration of air bubbles into the collected clarified water and, therefore, improves the quality of the collected clarified water.

An example of a first embodiment of a water treatment plant according to the method described here

The figure 3 presents an example embodiment of a plant for flotation treatment of water according to the invention.

Such an installation includes an inlet zone 31 of the treated water. The treated water is pre-coagulated and flocculated. To this end, the coagulation zone and the flocculation zone are arranged sequentially (not shown) upstream of the inlet zone 31.

A mixing zone 32 extends above the water inlet zone 31. The water inlet 31 and the mixing zone 32 are separated from each other by a panel 33, in which at least one part has openings 331. Preferably, the openings 331 extend over the entire surface of the perforated panel 33. Holes 331 made in the panel 33, can be, for example, round 15 cm in diameter. In other embodiments, the diameter of the hole 331 may be different. The diameter should preferably be from 2 to 50 cm.

The wall 34 separates the inlet water zones 31 and the mixing zones 32 from the flotation zone 35. This wall 34 is mainly vertical in its lower part and has an upper part 341, inclined at an angle in the direction of the flotation zone 35. The value of this angle is preferably from 120 ° to 175 °. The use of this inclined portion 341 allows, in particular, to facilitate the passage of water from the mixing zone to the flotation zone.

Alternatively, the inclined portion 341 may be replaced by a curved portion 342 (shown by the dotted line in FIG. 3), the radius of which may be between 0.1 and 1 m.

Such a water treatment plant according to the method described herein also includes means for collecting clarified water. These means include a chamber 36, the upper surface 361 of which is perforated at least partially, thus allowing clarified water to pass through this surface. In addition, the chamber 36 is connected to a pipe 37, which extends beyond the flotation zone 35 in the direction of the spillway (not shown), or any other means that allows the clarified water obtained after the flotation treatment to be withdrawn.

In an alternative embodiment of the construction described here, the perforated chamber 36 may be replaced by a perforated conduit located at the bottom of the flotation zone 35.

The vertical partitions 39 are installed mainly vertically in the flotation zone 35. The height of these partitions 39 can be from 30 to 300 cm. These partitions 39 are continuous and can be installed at equal or unequal intervals. For example, they can be located in the range from 30 to 300 cm.

Note that the closer the baffle plate 39 is to the wall 34, the smaller the interval separating them. This prevents the appearance of induced rotation of the fluid 102 between the two plates 39, as shown in figure 10.

In other exemplary embodiments, partitions 39 may be perforated. This, in particular, allows to improve the distribution of clarified water over the entire horizontal surface of the treated water intake zone. In addition, it is possible to make these partitions 39 replaceable, in particular, in order to facilitate maintenance of the device operating according to the method described here. In addition, these partitions 39 are preferably made of high quality steel. In alternative designs, they can be made of materials such as plastic. This can be especially beneficial when treating seawater.

In alternative embodiments of the method described herein, partitions 39 may also have a part 391 that is inclined relative to the vertical by an angle, the magnitude of which can be in the range from 120 to 240 °, as shown by the dotted line in figure 3. They can also be inclined along their entire length . In another alternative, the partitions 39 may have a curved portion 392 (indicated by a dotted line) in the direction of the wall 34 or in the other direction. The use of this inclined 391 or curvilinear part 392 allows to improve the breakdown of the reverse flows in the intake zone of purified water.

In addition, the mixing zone 32 has at least one spray nozzle 40 of pressurized water located near the perforated panel 33.

In this exemplary embodiment, nozzles 40 are positioned along the axis of each hole 331 in the panel 33, as shown in FIG. 3. The diameter of the hole 331 is preferably in the range of 5 to 50 cm. This allows for an optimal mixture of the flow of treated water and pressurized water.

However, as an alternative to this embodiment, in which the holes 331 made in the perforated panel 33 have a small diameter, preferably from 2 to 30 cm, no connection between each nozzle and perforation 331 is required, as shown in FIG. 4.

As will be explained in more detail below, these spray nozzles 40 make it possible to create an initially falling stream of pressurized water and then relieve the pressure of the water in the mixing chamber 32. In this case, the pressure water is sprayed in the mixing chamber 32 in countercurrent to the treated water.

In an alternative to this embodiment, the spray nozzle 40 may be configured such that it initially generates an upward flow of pressurized water in the mixing zone. In this case, pressurized water is sprayed in the mixing chamber in a parallel flow of the treated water.

These spray nozzles 40 are connected to pressurized water receiving means 42 through pipes 41. Pressurized water receiving means 42 are connected to a compressed air cylinder (not shown) provided with one or more air ejectors that provide an air-water mixture. These means for producing pressurized water are, on the one hand, connected to a conduit 37 through which clarified water flows, by a pipe 43, and, on the other hand, to an air supply 44. Thus, pressurized water is obtained, preferably from 3 to 8 bar, using part of the collected clarified water and air.

As will be explained below in more detail, means for producing water under pressure can be placed in parallel in order to ensure atomization of water under pressure with different flow rates.

The figure 5 shows an example of a spray nozzle 40.

Note that the principle of operation of these spray nozzles 40 consists of a double pressure relief, similar to WRC nozzles. However, several characteristics distinguish spray nozzles 40 from WRC nozzles. Spray nozzles 40 are connected to two inlets of pressurized water flowing with different flows Q1 and Q2. Thus, they take into account the spraying of water under pressure with flow rates Q1, Q2, Q1 + Q2.

As shown in the drawings, such spray nozzles 40 have a main hollow body 51, one end of which provides a first perforated pressure relief wall 52 and a second perforated pressure relief wall 53 that are parallel to each other at a certain distance, thereby creating an intermediate chamber . The holes made in the first wall 52 to reduce the pressure and in the second wall 53 of the decrease in pressure, distributed mainly uniformly over their entire surface. The density of the holes of the first pressure reducing wall 52 is less than the density of the holes of the second pressure reducing wall 53. In addition, the surface of the holes made in the first pressure reducing wall 52 is larger than the surface of the holes made in the second pressure reducing wall 53. The diameter of these holes is from 1 to 15 mm.

In addition, the lower end of the main part 51 forms an angle relative to the vertical. The value of this angle lies between 0 and 20 °. According to one alternative to the method described here and shown in figure 5, the lower part of the main body 51 is curved. The fact that the main body 51 has an expanding shape facilitates spraying.

The main body 51 includes a secondary hollow body 54. This secondary hollow body 54 intersects with the first pressure water stream at flow rate Q1, while the main hollow body 51 intersects with the second pressure water flow at flow rate Q2, preferably of a higher value. In an alternative solution, this flow rate Q2 may also have a smaller value.

In this embodiment, each spray nozzle 40 is connected to two pressurized water distribution networks supplying pressurized water at flow rates Q1 and Q2. Thus, the means 42 for supplying water under pressure are separated (not shown), which allows for three flow rates Q1, Q2 and Q1 + Q2 of water under pressure.

As specifically shown in figures 4, 6 and 6 bis, several rows 45 of the plurality of spray nozzles 40 may be arranged in parallel.

6 is a diagram of an exemplary architecture of a pressure water distribution network consisting of two rows of 45 spray nozzles 40.

Such a network includes two pressure water distribution networks with flow rate Q1 and two pressure water distribution networks with flow rate Q2, using two rows of spray nozzles.

As shown in the drawing, each spray nozzle 40 of each row 45 is connected to a first pressure water distribution network with a flow rate Q1 through a pipe 41 and to a second pressure water distribution network with a flow Q2 through a pipe 41.

An alternative solution, shown in figure 6 bis, is to use two rows of spray nozzles 40, without dividing the distribution network into Q1 and Q2.

The water purification apparatus of the method described herein further includes a scraper (not shown). As described in more detail below, such a scraper allows the removal of sludge consisting of suspended solids, organic matter, algae originally present in raw water, emerging in the upper part of mixing zone 32 and flotation zone 35, as well as air bubbles introduced into structure outside the flotation zone (arrow 1) in the means of regeneration 46.

An example of a second embodiment of a water treatment plant according to the method described here

With reference to figures 7-9 below, a second example of an embodiment of a water treatment plant according to the claimed method is described.

In this second embodiment, the water treatment plant has a number of characteristics inherent in the characteristics of the apparatus of the first embodiment described above. Here, only differences between the first and second examples of the embodiment of the installation will be described.

As shown in FIG. 7, this second embodiment uses a perforated plate 71 located downstream of the perforated panel 33 in the mixing zone 32. This perforated plate 71 is installed so that the intermediate portions 711 are formed in the solid parts of the perforated panel 33. In other words, the intermediate holes 711 and the holes 331 do not match and form deflectors, which are clearly visible on 7 and 8.

The intermediate holes in the perforated plate 71 may have a diameter of 2 to 50 cm. In addition, the perforated panel 33 and the perforated plate 71 are preferably separated by a distance of 1/3 to 3 of the diameters of the intermediate holes 711.

In this second embodiment, one or more spray nozzles 40 may be used. Each spray nozzle 40 need not be located along the axis of the intermediate hole 711.

As in the embodiment described above, an alternative for this embodiment may be to use several rows 45 of spray nozzles 40, as shown in FIG. 8.

The spray nozzles used in this second embodiment may be similar to the spray nozzles 40 described above with reference to figures 5 and 6.

In an alternative to this second embodiment shown in FIG. 9, the spray nozzles are different from the spray nozzles 40 described above in that each of them is not connected to a first pressurized water spray network with a flow rate of Q1 and a second pressurized water spray network Q2. In contrast, the spray nozzles used in this alternative example of the second embodiment are divided into two categories:

- in the spray nozzles 91 of the first category, each of them is connected to a network for spraying water under pressure with a flow rate of Q1;

- in the spray nozzles 91 of the second category, each of them is connected to the network of a spray of water under pressure with a flow rate of Q2.

These spray nozzles 91 and 92, for example, may be of type WRC or any other type in accordance with the principle of creating air bubbles.

In another alternative, the nozzles 40 are all identical and the sprayer has only one flow rate.

In an alternative example of this embodiment, shown in figure 8 bis, the perforated plate may have two types of intermediate holes:

main intermediate holes and cleaning intermediate holes 712.

The main intermediate holes consist of holes 711 arranged so that the perforated plate 71 includes a mudguard. The cleaning intermediate holes 712 are made in solid parts connecting the main intermediate holes 711 of the perforated plate 71. Using these cleaning holes 712 allows you to optimize the homogenization of the flow of the treated water entering the mixing zone 32.

The diameters of the main intermediate holes 711 and the cleaning intermediate holes 712 are selected so that the flow rate through the main intermediate holes 711 is equal to the flow rate through the cleaning intermediate holes 712.

The flotation treatment method for water according to the process described here

The following describes a method of purifying water by flotation.

Such a method consists in feeding treated water to a water treatment plant according to the exemplary embodiments described above.

The treated water, which was previously subjected to coagulation and flocculation, is supplied to the inlet zone 31. Then, the treated water is introduced upstream into the mixing zone 32, passing through the holes 331 of the perforated panel 33.

At the same time, pressurized water is introduced into the mixing zone 32 through the spray nozzles 40, followed by depressurization in countercurrent to the upward flow of the treated water. As described above, pressurized water can also be introduced into the mixing zone in a parallel flow.

Water under pressure is obtained by activating means 42 for producing water under pressure, using part of the clarified water that is taken from the flotation zone 35, and air coming from an air source 44.

Pressurized water is supplied via line 41 to the spray nozzles 40. This water crosses the first pressure reduction wall 52. Water under pressure is subjected to pressure relief and expands. Subjected to pressure and depressurization, the water then crosses the second wall 53 of the pressure reduction and are subjected to a further pressure drop, leading to the spraying of water. This nebulization phenomenon helps to prevent strong droplet breaking during the nebulization stage.

Spraying under pressure and then relieving the pressure of water in the mixing zone 32 is accompanied by the formation of microbubbles of air uniformly distributed over the entire horizontal section of the mixing zone 32.

The fact that the treated water is introduced into the mixing zone 32 through the perforated panel 33 allows homogenizing and fragmenting the water flow, preventing the formation of short chains, reverse flow zones and dead zones. In other conditions, the use of perforated panel 33 allows for uniform contact of the treated water and air microbubbles over the entire horizontal section of the mixing zone 32.

The uniform contact of the treated water and air microbubbles can be further improved by inserting a plate with holes 71 between the perforated panel 33 and the spray nozzles.

Thus, the combination of homogenization of the flow of treated water using a perforated panel, with the placement of spray nozzles near each hole in the perforated panel and / or using a perforated plate forming a mudguard allows for an optimal mixture of treated water and water under pressure.

Microbubbles of air serve to supply to the surface of the mixing zone 32 and the flotation zone 35 of all particles in suspension in the treated water. Thus, the fact that the contact between the treated water and air microbubbles is uniform allows optimizing the clarification of the treated water, which mainly increases the efficiency of flotation treatment of water.

A mixture of microbubbles of air with agglomerated particles that were initially suspended in the treated water is then forced to the top of flotation zone 35, as indicated by arrow J. This mixture can then be removed outside the flotation zone 35 using a scraper (not shown), which allows you to clean the surface of the flotation zone 35 and to direct the resulting slurry and air bubbles in the means of regeneration 46, in the direction shown by arrow I.

Thus, the clarified water flows in the direction of the lower part of the flotation zone 35, which has a chamber 36 and meets with partitions 39. With these partitions 39, the stream of clarified water is divided into fragments.

Due to the fact that the partitions 39 fragment the flow of clarified water in the flotation zone 35, eliminates the appearance of reverse flows in the intake zone of purified water.

This is reflected in figure 10, which shows the vectors of the fluid flow rate 101 in the inner part of the flotation zone 35.

A comparison of figures 2 and 10, which respectively show the liquid velocity vectors in the inner part of the flotation zone of the installation according to the known technology and the installation according to the method described here, allows a better understanding of the changes in the liquid flow resulting from the use of baffles 39 in the flotation zone 35.

This is shown in figure 2, in which the velocity vectors 21 are concentrated in the form of a vortex in the center of the flotation zone. This vortex creates reverse flows and directs clarified water to the upper part of the flotation zone, where it mixes with a layer of microbubbles.

On the other hand, FIG. 10 shows that the fluid velocity vectors are broken at the partitions 39 and that the velocity vectors located between these partitions 39 are not broken, i.e. they do not rise towards the top of the flotation zone.

Thus, the use of such baffles 39 allows to prevent the phenomenon of reverse flows in the lower part of the flotation zone, in which the chamber 36 is located, allowing the selection of clarified water, and, therefore, to prevent or at least limit the output of microbubbles of air along with clarified water.

The use of partitions 39 allows to prevent the entry of bubbles and sludge into the clarified water intake line and, therefore, to prevent contamination of the collected clarified water by microbubbles of air loaded with solid particles.

Therefore, the method according to the invention allows to optimize clarification of water by flotation and to improve the quality of clarified water collected at the end of the flotation treatment cycle.

In addition, the method according to the invention may also include a step consisting of selecting a flow rate of pressurized water introduced into the mixing zone. The choice of the magnitude of the flow rate of water under pressure may be related to the flow rate of the treated water and / or the quality of the treated water. Indeed, if the flow rate of the treated water varies in the range from 1 to 4, and / or if the quality of the treated water changes, it is, in particular, of economic interest to be able to change the flow rate of pressure water in the same proportions.

Similarly, when the flow rate of the treated water is quite low and / or the quality of the treated water is sufficiently high, a means for producing pressurized water is turned on depending on the flow rate Q1.

When the flow rate of the treated water is increased and / or when the quality of the treated water is high, the means for producing pressurized water will work depending on the flow rate Q2, or all means for producing water will be used to ensure a flow rate equal to the sum of Q1 and Q2.

Claims (34)

1. Installation for water purification by flotation, containing:
- one inlet zone of the treated water (31), which was previously subjected to coagulation and flocculation;
- one mixing zone (32) of water under pressure and then under vacuum with the specified treated water;
- one flotation zone (35), separated from the specified mixing zone (32) by the wall (34);
- one zone of intake of purified water (36) provided in the lower part of the specified flotation zone (35);
characterized in that said mixing zone (32) comprises at least one spray nozzle (40, 91, 92) of said water under pressure, said spray nozzle (40, 91, 92) being installed near the panel (33), at least one part of which has openings (331) and which separates said inlet zone (31) and said mixing zone (32). 2. Installation for water purification according to claim 1, characterized in that the said panel (33) is installed mainly horizontally. 3. Installation for water purification according to claim 1, characterized in that the said panel (33) is installed mainly vertically. 4. Installation for water purification according to claim 1, characterized in that the plate forming the mudguard (71) is mainly mounted parallel to the specified panel (33), and in which at least one part has first openings (711) passing between the specified panel (33) and the specified nozzle (40, 91, 92). 5. Installation for water purification according to claim 4, characterized in that the first holes (711) of said plate (71) pass through the solid parts of said panel (33). 6. Installation for water purification according to claim 5, characterized in that in said plate forming a mudguard (71), there is a second hole (712), which is located as an extension of said holes (331) of said panel (33). 7. Installation for water purification according to claim 1, characterized in that each of these spray nozzles is located mainly along the axis of one of these holes (331) of said panel (33). 8. Installation for water purification according to claim 1, characterized in that it includes a first (41) and second (41 ') distribution network for the distribution of the specified water under pressure in accordance with two different flow rates. 9. Installation for water purification according to claim 8, characterized in that said nozzles (40, 91, 92) are connected to said first (41) and second (41 ') distribution networks. 10. Installation for water purification according to claim 8, characterized in that it contains at least two of these nozzles (91, 92), which belong to two categories of nozzles, while the first category of nozzles is connected to the specified first network (41) and the second category of nozzles is connected to the specified second network (41 '). 11. Installation for water purification according to claim 1, characterized in that said nozzles (40, 91, 92) include two perforated plates separated from each other. 12. Installation for water purification according to claim 1, characterized in that said nozzles (40, 91, 92) in the lower part are made diverging. 13. Installation for water purification according to item 12, characterized in that the angle of deviation of the lower part of the nozzle from the vertical is 0 ° to 20 °. 14. Installation for water purification according to item 12, characterized in that the deviation of the lower part of the nozzle is made on a curve. 15. Installation for water purification according to claim 1, characterized in that the upper part of the indicated wall (34) separating the specified mixing zone (32) from the specified flotation zone (35) has a part (341), inclined at an angle in the direction of the specified flotation zones (35). 16. Installation for water purification according to clause 15, characterized in that the value of the specified angle lies in the range from 120 ° to 175 °. 17. Water treatment plant according to claim 1, characterized in that said wall (34) separating said mixing zone (32) from said flotation zone (35) has an upper part (342) that is curved in the direction of said zone flotation (35). 18. Installation for water purification according to claim 17, characterized in that said curvilinear part (342) has a radius of curvature from 0.1 to 1 m. 19. A water treatment plant according to claim 1, characterized in that said flotation zone (35) has a plurality of partitions (39) extending substantially vertically above said water intake zone (36). 20. Installation for water purification according to claim 19, characterized in that at least one of these partitions (39) has at least one upper part (931), inclined at an angle, or a curved part ( 392). 21. Installation for water purification according to claim 20, characterized in that said angle has a value from 120 ° to 240 °. 22. Installation for water purification according to claim 19, characterized in that the said partitions (39) have a height of from 30 to 300 cm 23. Installation for water purification according to claim 19, characterized in that said partitions (39) are located in close proximity to each other near said wall (34), separating said mixing zone (32) from said flotation zone (35). 24. Installation for water purification according to claim 19, characterized in that the said partitions (39) are separated from each other by a distance of from 20 to 300 cm 25. Installation for water purification according to claim 1, characterized in that said intake zone has means (36) for collecting clarified water connected to a means for collecting clarified water. 26. Installation for water purification according to claim 1, characterized in that it contains a means (42) for producing said water under pressure. 27. A water treatment plant according to claim 26, characterized in that said means (42) for producing water under pressure is connected to said means (36) for taking clarified water and to an air supply source (44). 28. Installation for water purification according to claim 1, characterized in that it contains means for cleaning the upper part of the specified flotation zone (35). 29. A method of purifying water by flotation, characterized in that it consists of transferring water to the installation according to claim 1 and introducing into the said mixing zone (32) an upward flow of said treated water through said perforated panel (33) and a stream of said water under pressure using said spray nozzles (40, 91, 92), thus forming air bubbles capable of bringing particles in suspension in said treated water to the surface of said mixing zone (32). 30. The flotation water treatment method according to Claim 29, wherein said stream of said water under pressure is initially upward. 31. The method of purification of water by flotation according to clause 29, wherein the specified stream of the specified water under pressure is initially downward. 32. The flotation water treatment method according to clause 29, wherein said stream of said water under pressure is initially horizontal. 33. The flotation water treatment method according to clause 29, wherein the selection of the flow rate of water under pressure is carried out depending on the flow rate of said treated water and / or the quality of said treated water. 34. The flotation water treatment method according to clause 29, further comprising cleaning by removing particles collected by air bubbles outside the flotation zone (35).

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